Posted by BRENDAN on .
Please show the quickest way to do this question?
Amanda has 20 coins in her purse. She has only 10c,20c and 50c coins, and their total value is $5. If she has more 50c than 10c coins, how many 10c has she?
Thank You

MATHS 
Dean,
Are you in algebra using variables 'c'?

MATHS 
BRENDAN,
I'm not sure what you mean.

MATHS 
Dean,
What grade are you in?

MATHS 
BRENDAN,
YEAR 4

MATHS 
Dean,
c stands for cents?

MATHS 
BRENDAN,
yes c stands for cents.

MATHS 
Dr Russ,
I got 4 x 50c = $2
2 x 10c = 20 c
14 x 20c = $2.80c
so she has 2 x 10c 
MATHS 
Reiny,
Since you are in year 4, you will be able to solve this algebraically.
let the number of 10c pieces be x
let the number of 20c pieces be y
let the number of 50c pieces be (20xy)
10x + 20y + 50(20xy) = 500
reduces to
4x + 3y = 50
so we need positive integer solutions for x and y
clearly x has to be between 0 and 13
after only two tries, I got
x = 2, and y = 14
then
number of 10c pieces = 2
number of 20c pieces = 14
number of 50c pieces = 20214 = 4
check: 2x10 + 14x20 + 4x50 = 500